Fair Value of Financial Instruments - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	$ 796,696,304	$ 818,340,970
Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	796,696,304	818,340,970	$ 782,862,049
Bond Purchase Commitment [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	431,879
Bond Purchase Commitment [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	431,879
Taxable Mortgage Revenue Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	1,510,437	1,383,237
Taxable Mortgage Revenue Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	1,510,437	1,383,237	1,409,895
Derivative Financial Instruments (Reported within Other Assets) [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	321,503	10,911
Derivative Financial Instruments (Reported within Other Assets) [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	321,503	10,911
Public housing capital fund trusts [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value		43,349,357
Public housing capital fund trusts [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		43,349,357	$ 48,672,086
Mortgage Revenue Bonds Held In Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	768,468,644	743,587,715
Mortgage Revenue Bonds Held In Trust [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	768,468,644	743,587,715
Mortgage Revenue Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets at Fair Value	25,963,841	30,009,750
Mortgage Revenue Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 25,963,841	$ 30,009,750